Short communication: little change takes place in Camembert-type cheese water activities throughout ripening in terms of relative humidity and salt
Leclercq-Perlat, Marie Noelle | Helias, Arnaud | Corrieu, Georges | Génie et Microbiologie des Procédés Alimentaires (GMPA) ; Institut National de la Recherche Agronomique (INRA)-AgroParisTech
Water activity (a(w)) affects the growth and activity of ripening microorganisms. Moreover, it is generally accepted that a(w) depends on relative humidity (RH) and salt content; these 3 variables were usually measured on a given day in a cheese without the microorganism layer and without accounting for a distinction between the rind, the undeirind, and the core. However, a(w) dynamics have never been thoroughly studied throughout cheese ripening. Experimental Camembert cheeses were ripened under controlled and aseptic conditions (temperature, gaseous atmosphere, and RH) for 14 d. In this study, only RH was varied. Samples were taken from the cheese (microorganism layer) air interface, the rind, and the core. The a(w) of the cheese air interface did not change over ripening when RH varied between 91 and 92% or between 97 and 98%. However, on d 5, we observed a small but significant increase in a(w), which coincided with the beginning of growth of Penicillium camemberti mycelia. After d 3, no significant differences were found between the a(w) of the cheese air interface, the rind, and the core. From d 0 to 3, cheese rind a(w) increased from 0.94 to 0.97, which was probably due to the diffusion of salt from the rind to the core: NaC1 content in the rind decreased from 3.7 to 1.6% and NaC1 content in the core increased from 0.0 to 1.6%. Nevertheless, a(w) did not significantly vary in the core, raising questions about the real effect of salt on a(w).
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